Disclosed herein is an ink jet ink composition for digital manufacturing of transparent objects. Further disclosed is a curable ink comprising at least one monomer, oligomer, or prepolymer; an optional photoinitiator; an optional colorant; and an amide gellant having a molecular weight of from about 800 to about 2,500 g/mole; wherein the ink has an onset of gelation defined by the glass transition of the amide gellant according to the relationship Onset of Gelation (K)=(Constant) Tg of gellant (K); wherein the Constant is less than 1.5.
Still further disclosed is a process for printing a three-dimensional article comprising providing a curable ink comprising at least one monomer, oligomer, or prepolymer; an optional photoinitiator; an optional colorant; and an amide gellant having a molecular weight of from about 800 to about 2,500 g/mole; wherein the ink has an onset of gelation defined by the glass transition of the amide gellant according to the relationship Onset of Gelation (K)=(Constant) Tg of gellant (K); wherein the Constant is less than 1.5; depositing the curable ink in one or more layers; and curing the deposited ink to form the three-dimensional object.
Three-dimensional (3D) printers are becoming increasingly popular in home and professional applications. There are many advantages to using 3D printers, including quicker, more economical and high throughput prototype evaluation. 3D printers currently offer a number of solutions for selective deposition modeling for professional use.
A typical printing system applies an ultra-violet (UV) curable hot melt material to a non-curable wax support via inkjet. Each layer, typically microns in size, is cured after deposition. When the fabrication is complete, the support material is washed, melted or blasted away, depending on its composition, leaving the 3D fabrication. The UV curable materials are available in a wide variety of physical characteristics (e.g., tensile strength, tensile modulus, flexural strength, and the like), but in a limited number of colors, and using different colors presents a particular challenge due to differing rates of curing and final curing hardness value which may preclude printing articles with multiple colors. Many of the current materials are available in a limited number of colors, and many of the materials are not transparent and are often slightly yellow in color even in the absence of colorants.
Further, additive manufacturing as practiced in industry has been, to date, mostly concerned with printing structural features using conventional curable ultra-violet (UV) inks when a multi-jet modeling (MJM) process is used. In MJM process, liquid monomer is jetted onto a substrate layer by layer, interspersed with a curing step by UV light to build up a three-dimensional object over time. Objects that have overhangs require a support layer that is jettable, curable, and removable after the object has been formed. This approach is used, for example, to print clear, glass-like, transparent, and/or colored objects. However, these objects often are yellowing with time or are not completely clear. Early attempts at making objects from UV gel inks has in some cases produced opaque samples and/or objects that are yellow or that have yellowed with time.
U.S. patent application Ser. No. 14/630,629, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof a color three-dimensional (3D) printing system including (1) a solid build ink for each of a plurality of colors, wherein each solid build ink includes (a) a solid acrylate in an amount from about 40 to about 70 percent by weight, (b) a non-curable wax in an amount from about 10 to about 45 percent by weight, (c) a curable wax in an amount from about 1 to about 15 percent by weight, (d) a photoinitiator, and (e) a colorant; each solid build ink has a curing speed adjusted by a ratio of the non-curable wax to curable wax such that the initial curing speed and final hardness of each solid build ink is approximately the same for each of the plurality of colors, and (2) a support material including the non-curable wax used in each build ink, the support material providing a scaffold for deposition of each build ink.
U.S. Pat. No. 8,882,256, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof curable solid inks which are solid at room temperature and molten at an elevated temperature at which the molten ink is applied to a substrate. In particular, the curable solid inks comprise low molecular weight amide gellants that impart self-leveling capabilities to the inks. Also disclosed are methods for making the amide gellant and the inks comprising the amide gellants.
U.S. Pat. No. 8,916,084, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof a method for fabricating a three-dimensional object including depositing a first amount of an ultraviolet curable phase change ink composition comprising an optional colorant and a phase change ink vehicle comprising a radiation curable monomer or prepolymer; a photoinitiator; a reactive wax; and a gellant upon a print region surface; successively depositing additional amounts of the ultraviolet curable phase change ink composition to create a three-dimensional object; and curing the ultraviolet curable phase change ink composition.
Currently available ink compositions are suitable for their intended purposes. However, a need remains for improved ink compositions that are clear and that do not yellow upon curing. Further, a need remains for improved ink compositions suitable for three-dimensional printing of clear objects. Still further, a need remains for improved compositions suitable for three-dimensional printing of clear objects that do not yellow with age.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.